|Publication number||US20070299490 A1|
|Application number||US 11/555,111|
|Publication date||Dec 27, 2007|
|Filing date||Oct 31, 2006|
|Priority date||Jun 23, 2006|
|Also published as||EP2077896A2, EP2077896B1, WO2008036865A2, WO2008036865A3|
|Publication number||11555111, 555111, US 2007/0299490 A1, US 2007/299490 A1, US 20070299490 A1, US 20070299490A1, US 2007299490 A1, US 2007299490A1, US-A1-20070299490, US-A1-2007299490, US2007/0299490A1, US2007/299490A1, US20070299490 A1, US20070299490A1, US2007299490 A1, US2007299490A1|
|Inventors||Zhongping Yang, John L. Sommer, James D. Reinke|
|Original Assignee||Zhongping Yang, Sommer John L, Reinke James D|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (2), Referenced by (31), Classifications (7), Legal Events (2)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This application is a continuation-in-part of U.S. patent application Ser. No. 11/426,207 filed on Jun. 23, 2006, entitled “ELECTRODE SYSTEM WITH SHUNT ELECTRODE”, to Volkert A. Zeijlemaker, incorporated herein by reference in its entirety. This application also claims priority to U.S. Provisional Application Ser. No. 60/826,476, filed Sep. 21, 2006
The invention relates to medical devices and, more particularly, to implantable medical device leads for use with implantable medical devices (IMDs).
In the medical field, implantable leads are used with a wide variety of medical devices. For example, implantable leads are commonly used to form part of implantable cardiac pacemakers that provide therapeutic stimulation to the heart by delivering pacing, cardioversion or defibrillation pulses. The pulses can be delivered to the heart via electrodes disposed on the leads, e.g., typically near distal ends of the leads. In that case, the leads may position the electrodes with respect to various cardiac locations so that the pacemaker can deliver pulses to the appropriate locations. Leads are also used for sensing purposes, or for both sensing and stimulation purposes. Implantable leads are also used in neurological devices, muscular stimulation therapy, and devices that sense chemical conditions in a patient's blood, gastric system stimulators.
Occasionally, patients that have implantable leads may benefit from a magnet resonance image being taken of a particular area of his or her body. Magnetic resonance imaging (MRI) techniques achieve a more effective image of the soft tissues of the heart and vascular system. MRI procedures can also image these features without delivering a high dosage of radiation to the body of the patient, and as a result, MRI procedures may be repeated reliably and safely. However, MRI devices may operate at frequencies of 10 megahertz or higher, which may cause energy to be transferred to the lead. In particular, the high frequency fields induce a voltage in the lead, causing the potential of the lead to be higher than the surrounding tissue. In effect, the lead behaves as an antenna. Current may flow from the electrode into the tissue proximate to the electrode due to induced voltage. It is therefore desirable to develop a lead addresses this disadvantage.
Aspects and features of the present invention will be appreciated as the same becomes better understood by reference to the following detailed description of the embodiments of the invention when considered in connection with the accompanying drawings, wherein:
The present invention is directed to a medical lead, techniques for manufacturing such a lead, and systems that include a medical device coupled to a medical lead according to the present invention. The medical lead of the present invention includes a radio frequency signal (RF) shunted sleeve head (also referred to as a capacitive shunt). The RF shunted sleeve head is coupled to a lead body and to the tip electrode. The RF shunted sleeve head comprises a biostable dielectric coating introduced over the conductive element.
The medical lead is able to effectively manage high frequency signals from other devices such that the operation of a medical lead is not detrimentally affected. For example, the electrode assembly of the medical lead shunts the high frequency RF signals (e.g. 21 megaHertz (Mhz) to 128 MHz) generated from a magnetic resonance imaging (MRI) machine away from the tip electrode and into the larger area of the RF shunted sleeve head. This in turn, reduces the current density in the tissue near the electrode and reduces the level of heating. Consequently, a patient with a medical lead may undergo an MRI procedure without significantly affecting the operation of the medical lead.
RF-shunted sleeve head 201 is electrically connected to a conductive electrode shaft 203 via two parallel conductive rings 224 (e.g. C-rings etc.) and a conductive sealer 212 (also referred to as a sealing washer). At a proximal end 206 of electrode assembly 200, coil 230 is electrically coupled to conductive electrode shaft 203. RF shunted sleeve head 201 comprises a conductive element 202 surrounded or at least partially covered by an insulating material 204 (also referred to as a dielectric material). In one embodiment, conductive element 202 is cylindrically shaped (e.g. ring, etc.) or may possess other suitable shapes. Exemplary dimensions for conductive element 202 include a diameter of about 6.5 French (Fr.) by about 9 millimeters (mm) in length, an outer diameter of about 82 mils and an inner diameter of about 62 mils. Conductive element 202, in one embodiment, includes an increased diameter at the distal end and a reduced diameter at the proximal end of the conductive element 202. The surface area of conductive element 202 is about 60 mm2 which is much larger than the 5.5 mm2 surface area of electrode 207. A large surface area ratio, defined by the ratio of the surface area of conductive element 202 to the surface area of electrode 207, is desired to insure that current induced from a MRI machine is spread over a large area of electrode assembly 200. A tenfold (i.e. 10×) larger surface area ratio results in about tenfold lower temperatures at the tip of electrode 207 assuming ring electrode 216 has low impedance at high frequencies. Conductive element 202 comprises materials that are chemically stable, biocompatible, and x-ray transparent. Exemplary material used to form conductive element 202 includes titanium, titanium alloy, conductive polymers, and/or other suitable materials.
Conductive sealer 212 conducts current and also prevents fluid from passing through lumen 246. Referring to
Conductive sealer 212 comprises a polymer and a conductive polymer such as a conductive powder (e.g. carbon, carbon nanotube, silver, platinum etc.). The conductive polymer ranges from about 1% to about 25% of conductive sealer 212. The polymer (e.g. silicone etc.) is commercially available from Nusil Technology LLC, located in Carpinteria, Calif. Polyurethane is commercially available from The Polymer Technology Group Inc. located in Berkeley, Calif.
Conductive rings 224 are shaped, in one embodiment, as a C-ring to receive conductive sealer 212. Conductive rings 224 have an outer diameter of about 1.5 mm, an inner diameter of about 0.7 mm, and a thickness that ranges from about 0.25 mm (T1) to about 0.5 mm (T2). Conductive rings 224 are comprised of platinum or other suitable materials.
Bipolar shunted lead circuit 304 includes ring electrode 216, RF shunted sleeve head 201, and tip electrode 207. Capacitors C3, C4, and C5 correspond to ring electrode 216, sleeve head 201, and tip electrode 207, respectively. Resistors R1, R2, R3, and R4 represent the impedance created by tissue and/or blood of the patient. R1, R2, and R3 along with capacitors C5, C4, and C3 represent the electrode to tissue interface impedances. Generally, larger area electrodes result in larger values of capacitance and smaller values of resistance. However, the addition of an insulating material 204 over sleeve head 201 reduces the effect of electrode 207 to tissue interface impedances and its capacitance. In particular, C4 comprises a series capacitance of the electrode to tissue interface and capacitance due to insulation. Exemplary values for bipolar shunted lead circuit 304 include C3 at 10 microF (uF), R3 is 100 Ohm (Ω), R2 is 100Ω, C5 is 1 uF, R1 is 500Ω, and C4 is about 0.5 nanoFarad (nF) to about 10 nF. Optimally, C4 should possess a capacitance of about 1-2 nF.
Generally, under typical pacing conditions, pacing current (Ipacing current) flows from tip electrode 207 to ring electrode 216 and then returns to IMD circuit 302. Negligible or no current Ipacing current passes through the RF shunted sleeve head 201 and resistor R2 because under a low frequency or direct current (DC) application, capacitor C4 acts like an open circuit to a constant voltage across its terminals. A portion of the Ipacing current passes to the patient's tissue, represented as resistor R1, due to the large capacitance of C5 associated with tip electrode 207. Similarly, a portion of the Ipacing current passes to the patient's tissue, represented as resistor R3, due to the large capacitance of C3 associated with ring electrode 216.
Under MRI conditions, a large current (Itotal) is induced in the medical lead 106 and IMD circuit 402 due to the RF voltage sources VRF and VRF2. A portion of the current, I1, passes through the RF shunt sleeve head 201 represented by R2 and C4. Since the RF frequency is large, the impedance associated with C4 is small resulting in a large portion of the total current flowing through RF shunt sleeve head 201. The remainder of the current, 12, passes through tip electrode 207, represented by capacitor C5. The current then returns to capacitor C2 of IMD circuit 402 through ring electrode 216 and through the body tissue and housing 102. Because conductive element 202 of RF shunted sleeve head 201 has a large surface area relative to tip electrode 207, the total current is spread over a larger total surface area resulting in a lower current density. This results in reduced local heating at the tip of electrode 207. In sum, RF shunted sleeve head 201 and tip electrode 207 cooperate to serve as a high-pass filter, allowing only high frequencies signals to “pass” through conductive element 202 and low frequency signals are blocked. RF shunted sleeve head 201 serves as a capacitor and passes the MRI high frequency current into the blood stream (represented by R2 in
It is understood that the present invention is not limited for use in pacemakers, cardioverters of defibrillators. Other uses of the leads described herein may include uses in patient monitoring devices, or devices that integrate monitoring and stimulation features. In those cases, the leads may include sensors disposed on distal ends of the respective lead for sensing patient conditions.
The leads described herein may be used with a neurological device such as a deep-brain stimulation device or a spinal cord stimulation device. In those cases, the leads may be stereotactically probed into the brain to position electrodes for deep brain stimulation, or into the spine for spinal stimulation. In other applications, the leads described herein may provide muscular stimulation therapy, gastric system stimulation, nerve stimulation, lower colon stimulation, drug or beneficial agent dispensing, recording or monitoring, gene therapy, or the like. In short, the leads described herein may find useful applications in a wide variety medical devices that implement leads and circuitry coupled to the leads.
Various embodiments of the invention have been described. These and other embodiments are within the scope of the following claims. For example, electrode 207 may include variously shaped electrodes such as ring shaped or other suitable shapes. Additionally, skilled artisans appreciate that other dimensions may be used for the mechanical and electrical elements described herein. Moreover, it is expected that 100% of the RF power is able to be shunted away by the RF sleeve head by implementing the claimed embodiment as well as other features.
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US20060247684 *||Jun 8, 2006||Nov 2, 2006||Greatbatch-Sierra, Inc.||Band stop filter employing a capacitor and an inductor tank circuit to enhance mri compatibility of active medical devices|
|US20060247747 *||Apr 29, 2005||Nov 2, 2006||Medtronic, Inc.||Lead electrode for use in an MRI-safe implantable medical device|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US7734354||Aug 3, 2007||Jun 8, 2010||Advanced Neuromodulation Systems, Inc.||Stimulation lead, stimulation system, and method for limiting MRI induced current in a stimulation lead|
|US7941225 *||Apr 27, 2007||May 10, 2011||Medtronic, Inc.||Magnetostrictive electrical stimulation leads|
|US7941226||Apr 27, 2007||May 10, 2011||Medtronic, Inc.||Magnetostrictive electrical stimulation leads|
|US7962224||Feb 5, 2008||Jun 14, 2011||Advanced Neuromodulation Systems, Inc.||Stimulation lead, stimulation system, and method for limiting MRI-induced current in a stimulation lead|
|US8032230||Oct 9, 2008||Oct 4, 2011||Advanced Neuromodulation Systems, Inc.||Stimulation lead, stimulation system, and method for limiting MRI induced current in a stimulation lead|
|US8099171||Jun 30, 2009||Jan 17, 2012||Pacesetter, Inc.||Implantable medical lead configured for improved MRI safety and heating reduction performance|
|US8103347||Apr 25, 2008||Jan 24, 2012||Advanced Neuromodulation Systems, Inc.||Implantable pulse generator comprising MRI current limiting windings in header structure|
|US8170687||Aug 7, 2009||May 1, 2012||Pacesetter, Inc.||Implantable medical device lead incorporating insulated coils formed as inductive bandstop filters to reduce lead heating during MRI|
|US8214055||Jan 23, 2012||Jul 3, 2012||Advanced Neuromodulation Systems, Inc.||Implantable pulse generator comprising MRI current limiting windings in header structure|
|US8315715||Jul 2, 2012||Nov 20, 2012||Advanced Neuromodulation Systems, Inc.||Implantable pulse generator comprising MRI current limiting windings in header structure|
|US8406896||Jun 29, 2009||Mar 26, 2013||Boston Scientific Neuromodulation Corporation||Multi-element contact assemblies for electrical stimulation systems and systems and methods of making and using|
|US8406897||Aug 19, 2009||Mar 26, 2013||Boston Scientific Neuromodulation Corporation||Systems and methods for disposing one or more layers of material between lead conductor segments of electrical stimulation systems|
|US8412351||Jul 10, 2008||Apr 2, 2013||Medtronic, Inc.||System and method for shunting induced currents in an electrical lead|
|US8442651||Mar 5, 2010||May 14, 2013||Medtronic, Inc.||Medical device with self-healing material|
|US8478423||Apr 7, 2009||Jul 2, 2013||Boston Scientific Neuromodulation Corporation||Insulator layers for leads of implantable electric stimulation systems and methods of making and using|
|US8538553||Sep 23, 2010||Sep 17, 2013||Pacesetter, Inc.||MRI compatible implantable lead|
|US8543218||Oct 29, 2012||Sep 24, 2013||Advanced Neuromodulation Sytems, Inc.||Implantable pulse generator comprising MRI current limiting windings in header structure|
|US8544170||Sep 23, 2011||Oct 1, 2013||Advanced Neuromodulation Systems, Inc.||Method of fabricating a percutaneous stimulation lead|
|US8601672||Jul 30, 2010||Dec 10, 2013||Advanced Neuromodulation Systems, Inc.||Method for fabricating a stimulation lead to reduce MRI heating|
|US8644932||Oct 29, 2010||Feb 4, 2014||Medtronic, Inc.||Assessing a lead based on high-frequency response|
|US8868208||Jan 31, 2013||Oct 21, 2014||Medtronic, Inc.||MR-compatible implantable medical lead|
|US9014815||Oct 29, 2010||Apr 21, 2015||Medtronic, Inc.||Electrode assembly in a medical electrical lead|
|US9089695||Jan 31, 2013||Jul 28, 2015||Medtronic, Inc.||MR-compatible implantable medical lead|
|US9108066||Mar 10, 2014||Aug 18, 2015||Greatbatch Ltd.||Low impedance oxide resistant grounded capacitor for an AIMD|
|US20110034983 *||Feb 10, 2011||Pacesetter, Inc.||Implantable medical device lead incorporating a conductive sheath surrounding insulated coils to reduce lead heating during mri|
|US20120253437 *||Oct 4, 2012||Seifert Kevin R||Coupling mechanisms for use with a medical electrical lead|
|US20120253438 *||Oct 4, 2012||Wei Gan||Coupling mechanisms for use with a medical electrical lead|
|US20130004560 *||Jan 3, 2013||The Regents Of The University Of California||Polymer Nanofilm Coatings|
|EP2445433A1 *||Apr 26, 2010||May 2, 2012||Greatbatch Ltd.||Frequency selective passive component networks for active implantable medical devices utilizing an energy dissipating surface|
|WO2009117221A2 *||Feb 25, 2009||Sep 24, 2009||Medtronic, Inc.||System and method for shunting induced currents in an electrical lead|
|WO2011136826A1||Sep 20, 2010||Nov 3, 2011||Medtronic, Inc.||Active circuit mri/emi protection powered by interfering energy for a medical stimulation lead and device|
|U.S. Classification||607/116, 607/119|
|Cooperative Classification||A61N2001/086, A61N1/056, A61N1/3718|
|Nov 1, 2006||AS||Assignment|
Owner name: MEDTRONIC, INC., MINNESOTA
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:YANG, ZHONGPING, MR.;SOMMER, JOHN L., MR.;REINKE, JAMES D., MR.;REEL/FRAME:018462/0528
Effective date: 20061031
|May 23, 2012||AS||Assignment|
Owner name: MEDTRONIC, INC., MINNESOTA
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:ZEIJLEMAKER, VOLKERT;REEL/FRAME:028253/0427
Effective date: 20120523